The number of measurements within each sample. For this chart, all samples are assumed to be the same size. In this spreadsheet, the sample size must be between 2 and 25.
 The k-value is number of standard deviations (typically 3) that the upper and lower control limits are placed away from the center line.
 R-bar is the mean of the Ranges in the data table and is used as the center line for the R-Chart.
 The estimated process mean is calculated as the mean of the X-bar values from the data table. It is used as the Center Line for the X-bar Chart.
 The estimated process standard deviation.
 The Cp index is calculated as (USL-LSL)/(6*sigma) where sigma is the process standard deviation. You want Cp to be greater than 1.
 This is the standard deviation of the sample mean, calculated as the process standard deviation divided by the square root of the sample size.
 The CPU index is the upper capability index for when you are only given an upper spec limit, USL. You want CPU > 1
 The CPL index is the lower capability index for when you are only given a lower spec limit, LSL. You want a CPL > 1.
 The Cpk index is used when the process mean is shifted away from the target value, or the point half way between the spec limits. It is the minimum of the CPU and CPL. You want a Cpk>1.
 Percent Yield measures the proportion of the output that is within the spec limits, assuming a Normal population distribution.
 Probability of a Type I Error (a):
If a sample value falls outside the control limits, we would conclude that the process is out of control. A Type I error is made when the process is concluded to be out of control when it is really in control. This probability is calculated assuming a normal distribution for the process.
 In-Control Average Run Length:
If the process is in-control, the ARL is the number of samples, on average, you would observe before getting an out-of-control signal. In other words, you expect to get a false alarm (a point outside the control limits) every N samples, where N is the ARL.
 X-bar is the sample mean calculated as the sum of the observations divided by the number of observations in the sample (n).
 The range for each sample is calculated as the Max value minus the Min value.